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The synthesis of bimetallic nanocatalysts with strained crystal lattices has attracted considerable interest. This is because, beyond the electronic structure modifications realized through elemental doping, the strain effect offers an extra mechanism to fine-tune the electronic structures, thereby possibly improving the catalytic performances. We present a method for constructing defective AuPd@Pd short nanowires, achieved through a controlled galvanic replacement reaction between short AuCu nanowires and Pd precursors. Advanced structural analyses using spherical aberration-corrected transmission electron microscopy (AC-TEM) validated the expanded crystal lattice on the nanowire surface and also demonstrated pronounced plasmonic absorption in the UV-vis region. Leveraging both plasmonic absorption and strain effects, the AuPd@Pd short nanowires displayed a higher apparent rate constant compared to Pd nanoparticles. Integrating molecular dynamic simulations with density functional theory calculations revealed that the tensile strain on AuPd@Pd short nanowires benefited the catalytic activity by elevating the d-band center, thereby intensifying the adsorption of p -nitrophenol. The current research introduces a unique method for synthesizing noble metal nanocrystals with specific dimensions and elucidates the rational development of high-performance plasmonic nanocatalysts through synergistic exploitation of the beneficial strain effect.

Concave nanocrystals stand out as a testament to the importance of the nanoscale morphology in dictating the functional properties of materials. In this report, we introduce a facile synthesis method for producing gold (Au) nanocrystals with a truncated octahedral morphology that features surface concavities (Au CNTOs). The incorporation of selenium (Se) doping into the truncated octahedral Au seeds was essential for their enlargement and the formation of concave structures. By simply adjusting the quantity of seeds, we could control the size of the nanocrystals while maintaining their distinctive morphology and surface concavity. The formation mechanism suggests that Se doping likely passivates the side faces, thereby slowing growth and promoting atomic deposition at the edges and corners. The resulting Se-doped Au CNTOs exhibited strong localized surface plasmon resonance (LSPR) absorptions in the visible spectrum and the SERS performance of their assemblies was demonstrated through crystal violet detection, reaching enhancement factors around 10 5 . This study presents an innovative approach to synthesizing concave Au nanocrystals through the incorporation of selenium during a seeded growth process, offering insights into the strategic design of plasmonic nanostructures.

Gold-based nanostructures with well-defined morphologies and hollow interiors have significant potential as a versatile platform for various plasmonic applications including biomedical diagnostics and sensing. In this study, we report the synthesis of Au@Ag core-shell nanocrystals with perfect octahedral shapes and tunable edge lengths via seeded growth. These nanocrystals were then oxidatively carved into yolk-shell nanocages with a retained octahedral morphology. The increase in octahedral edge length and volume of the interior hollow cavity synergistically leads to a red-shift of the LSPR peak. As a result, the optimized Au@AuAg yolk-shell octahedral nanocages showed a remarkable temperature increase of 23 °C upon 15 min irradiation of an 808 nm laser at a power density of 1 W cm -2 . This study provides a feasible strategy for creating octahedral AuAg nanostructures with tunable sizes and hollow interiors and validates their promising use in NIR photothermal conversion.

Non-noble metal photothermal materials have recently attracted increasing attention as unique alternatives to noble metal-based ones due to advantages like earth abundance, cost-effectiveness, and large-scale application capability. In this study, hierarchical copper sulfide (CuS) nanostructures with tunable flower-like morphologies and dimensional sizes are prepared via a fatty amine-mediated one-pot polyol synthesis. In particular, the addition of fatty amines induces a significant decrease in the overall particle size and lamellar thickness, and their morphologies and sizes could be tuned using different types of fatty amines. The dense stacking of nanosheets with limited sizes in the form of such a unique hierarchical architecture facilitates the interactions of the electromagnetic fields between adjacent nanoplates and enables the creation of abundant hot-spot regions, thus, benefiting the enhanced second near-infrared (NIR-II) light absorptions. The optimized CuS nanoflowers exhibit a photothermal conversion efficiency of 37.6%, realizing a temperature increase of nearly 50 °C within 10 min under 1064 nm laser irradiations at a power density of 1 W cm -2 . They also exhibit broad-spectrum antibacterial activity, rendering them promising candidates for combating a spectrum of bacterial infections. The present study offers a feasible strategy to generate nanosheet-based hierarchical CuS nanostructures and validates their promising use in photothermal conversion, which could find important use in NIR-II photothermal therapy.

Frame/skeleton-like nanostructures are of great value in plasmonic catalysis as a result of the synergetic structural advantages arising from both maximized surface atomic exposure and efficient incident light absorptions. Herein, we report the size-tunable fabrication of yolk-shell AuAg nanoparticles containing a spherical core and cuboctahedral skeletons (AuAg YSCNSs), together with the exploration of their applications for assisting the reduction of 4-nitrophenol (4-NP) under ultraviolet-visible (UV-vis) light irradiation. The use of glutathione (GSH) at an appropriate amount to mediate the galvanic replacement reaction between Au@Ag core-shell nanocubes and HAuCl 4 is found to be crucial in regulating the shape evolution. Their sizes could be readily tuned by altering the edge lengths of Au@Ag core-shell nanocubes. When working as the photocatalyst assisting the reduction of 4-NP, the AuAg YSCNSs exhibit a higher apparent rate constant under UV-vis light irradiation. The current work demonstrates the feasibility to create skeleton-like noble metal nanocrystals with the shape largely deviated from that of the original template via the "top-down" carving strategy by introducing non-metallic surface doping, which could be potentially extended to other noble metals or alloys.

To address the poor electronic conductivity and easily dissolved in electrolyte of polyoxometalates (POMs), and considering the high electrical conductivity and configuration advantages of crumpled graphene balls (CGBs), herein, a series of POM-based coordination polymers [Cu(pyttz) 2 ]PMo 12 @CGB (n, n=1, 2, 3) were successfully synthesized, and electrochemical lithium storage performance and lithium ion diffusion kinetics were comprehensively investigated. Galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) study confirm that [Cu(pyttz) 2 ]PMo 12 @CGB (n, n=1, 2, 3) integrates the advantage of high electronic conductivity of CGB and excellent Li + migration kinetics of POMs, which greatly ameliorates the electrochemical performances of POMs, among [Cu(pyttz) 2 ]PMo 12 @CGB (2) exhibits an excellent reversible specific capacity of around 941.4 mA h g -1 at 0.1 A g -1 after 150 cycles and admirable rate performance. This work will promote the development of POMCP anodes, thus fulfilling their potential in high-performance LIBs., (© 2023 Wiley-VCH GmbH.)

The formic acid oxidation reaction (FAOR) represents an important class of small organic molecule oxidation and is central to the practical application of fuel cells. In this study, we report the fabrication of Ir(IV)-doped PdAg alloy nanodendrites with sub-5 nm branches via stepwise synthesis in which the precursors of Pd and Ag were co-reduced, followed by the addition of IrCl 3 to conduct an in situ galvanic replacement reaction. When serving as the electrocatalyst for the FAOR in an acidic medium, Ir(IV) doping unambiguously enhanced the activity of PdAg alloy nanodendrites and improved the reaction kinetics and long-term stability. In particular, the carbon-supported PdAgIr nanodendrites exhibited a prominent mass activity with a value of 1.09 A mg Pd -1 , which is almost 2.0 times and 2.7 times that of their PdAg and Pd counterparts, and far superior to that of commercial Pt/C. As confirmed by the means of the DFT simulations, this improved electrocatalytic performance stems from the reduced overall barrier in the oxidation of formic acid into CO 2 during the FAOR and successful d-band tuning, together with the stabilization of Pd atoms. The current study opens a new avenue for engineering Pd-based trimetallic nanocrystals with versatile control over the morphology and composition, shedding light on the design of advanced fuel cell electrocatalysts.

We report a synthetic strategy to create gold(Au)-based "sphere-on-plate" hybrid nanostructures (SPHNSs). The surface doping of plate-like Au seeds with Pt/Ag atoms is found to be crucial to increase the lattice spacing, inducing island-like deposition of Au atoms via the Volmer-Weber growth mode. The resulting products are featured with the morphology that quasi-spherical nanoparticles are scattered over the nanoplates. Due to the presence of two distinctly dimensioned particles in one entity, the current Au-based SPHNSs exhibit unique dual plasmonic absorptions, where the visible absorbance centered at 546 nm is related to the size of the anchored particles. Arising from such a plasmonic advantage, the Au-based SPHNSs exhibit enhancement in photothermal conversion under laser irradiations at the wavelengths of both 808 and 1064 nm. The current work offers a feasible route to fabricate noble metal hybrid nanostructures involving zero-dimensional (0D) and two-dimensional (2D) structures, which could work as promising materials for photothermal conversion.

Gold-copper (Au-Cu) Janus nanostructures (Au-Cu Janus NSs) are successfully prepared using N-oleyl-1,3-propanediamine as capping agent and Cu(acac) 2 as the precursor in a typical seeded growth strategy. By preferably depositing Cu atoms on one side of concave cubic Au seeds, the Cu part gradually grows larger as more Cu precursors are added, making the size tuning feasible in the range of 74-156 nm. When employed as an electrocatalyst for electrochemical CO 2 reduction (CO 2 RR), the Au-Cu Janus NSs display superior performance to Au@Cu core-shell NSs and Cu NPs in terms of C 2+ products selectivity (67%) and C 2+ partial current density (-0.29 A cm -2 ). Combined experimental verification and theoretical simulations reveal that CO spillover from Au sites to the nearby Cu counterparts would enhance CO coverage and thus promote C-C coupling, highlighting the unique structural advantages of the Au-Cu Janus NSs toward deep reduction of CO 2 . The current work provides a facile strategy to fabricate tandem catalyst with a Janus structure and validates its structural advantages toward CO 2 RR, which are of critical importance for the rational design of efficient CO 2 RR catalyst., (© 2022 Wiley-VCH GmbH.)

Assembling two-dimensional noble metal nanocrystals into a three-dimensional mesoporous structure is of great value to solve the re-stacking issue for the practical application, which still remains a challenging technique. Herein, we report the one-pot fabrication of gold (Au) nanostructures with a crumpled paper ball-like morphology (Au NCPBs). The success of current work relies on the use of glutathione to crumple the branched Au nanosheets formed during the early stage, into spherical three-dimensional architecture, where the nanosheets are assembled with a mesoporous structure without intimate contact. When working as the agent toward photothermal conversion, the Au NCPBs exhibit enhanced photothermal conversion efficiency (η = 19.9%), as compared to that of flat and wrinkled Au nanosheets. Such an enhancement should be owing to the aggregation-induced effect, where the shortened inter-sheet distance contributes to an increased coupling between the plasmon oscillations/fields of the interacting Au nanosheets. The present study offers a feasible strategy to create spherical architecture of crumpled Au nanosheets and validates their structural advantage in photothermal applications, which could be potentially extended to other metals or alloys.

We report a facile synthesis of Au@Cu x O core-shell mesoporous nanospheres with tunable size in the aqueous phase via seeded growth. The success of the current work relies on the use of a halide-free copper (Cu) precursor and n-oleyl-1,3-propanediamine as a capping agent to facilitate the formation of a copperish oxide shell with a mesoporous structure and the presence of mixed oxidation states of Cu. By varying the amount of spherical Au seeds while keeping other parameters unchanged, their diameters could be readily tuned without noticeable change in morphology. As compared with commercial Cu 2 O, the as-prepared Au@Cu x O core-shell mesoporous nanospheres exhibit the higher adsorption ability, enhanced activity, and excellent stability toward photocatalytic degradation of methyl orange (MO) under visible light irradiation, indicating their potential applications in water treatment., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer NL declared a past co-authorship with one of the authors ML to the handling Editor., (Copyright © 2021 Zhang, Ma, Liu, Tong, Sha, Zhao, Liu and Zheng.)

We report a high-yield synthesis of gold (Au) nanosheets with tunable size and surface morphology in the aqueous phase. In particular, crumpled and flat Au nanosheets with a thickness of ∼10 nm could be selectively produced in high purity when the reaction was conducted at room temperature and in an ice-water bath, respectively. Unlike Au nanoplates/nanoprisms in the form of well-defined triangles or hexagons documented in previous studies, the current products exhibit random in-plane branches or holes, together with wavy edges. Strong absorbance in the NIR region was observed for all the Au nanosheet products. When serving as electrocatalysts for the ethanol oxidation reaction, the current products exhibited an enhanced activity and operation stability, as compared to quasi-spherical counterparts.

We report the fabrication of concave gold (Au) nanocrystals with a set of morphologies and controlled sizes via seeded growth. Starting with Au seeds with a well-defined morphology and uniform size, cubic and rodlike Au nanocrystals with a noticeable concave feature could be successfully obtained, respectively. We also track the growth process and record the shape evolution process. The effect of several reaction parameters on product morphology, such as capping agent and concentration of Ag + , are systematically investigated. Their optical and electrochemical properties are investigated via UV-vis extinction spectroscopy and cyclic voltammetry, respectively. Compared to spherical counterparts, the current concave Au nanocrystals exhibit a noticeable red shift of the absorbance peak in UV-vis extinction spectra and characterized electrochemical behavior of stepped facets, illustrating the morphological advantage.

The fast and reversible switching of plasmonic color holds great promise for many applications, while its realization has been mainly limited to solution phases, achieving solid-state plasmonic color-switching has remained a significant challenge owing to the lack of strategies in dynamically controlling the nanoparticle separation and their plasmonic coupling. Herein, we report a novel strategy to fabricate plasmonic color-switchable silver nanoparticle (AgNP) films. Using poly(acrylic acid) (PAA) as the capping ligand and sodium borate as the salt, the borate hydrolyzes rapidly in response to moisture and produces OH - ions, which subsequently deprotonate the PAA on AgNPs, change the surface charge, and enable reversible tuning of the plasmonic coupling among adjacent AgNPs to exhibit plasmonic color-switching. Such plasmonic films can be printed as high-resolution invisible patterns, which can be readily revealed with high contrast by exposure to trace amounts of water vapor., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The dynamic dual-stimuli-responsive surface wrinkles on a bilayer film with high bistability are unattainable and attractive for the applications of smart windows and optical displays. Here, we report a new strategy in developing moisture and temperature dual-responsive surface wrinkles on the polyvinyl alcohol/polydimethylsiloxane (PVA/PDMS) bilayer film by rationally designing the modulus changes of the PVA skin layer upon moisture and temperature. By optimizing the thickness of the PVA layer to 4.5 μm, the as-prepared surface wrinkles show long-awaited properties, such as fast response time, excellent reversibility without degradation of optical contrast, and high light transmittance modulation, which greatly outperforms the reported surface wrinkles. Moreover, the surface wrinkles on the bilayer film remain highly bistable without additional energy consumption for more than five months in ambient room conditions both in the opaque and transparent states. These promising dual-stimuli-responsive surface wrinkles on bilayer films hold great promises for various applications triggered by moisture and temperature, such as smart windows and rewritable optical displays.

We report a facile synthesis of wavy carbon nanowires (WCNWs) derived from polyurethane via KOH activation. The success of this synthesis relies on a carefully designed activation procedure, which involved one pre-activation stage to form suitable precursor and one high-temperature activation stage to allow directional carbon reconstruction. In particular, PU was initially mixed with KOH and thermally treated sequentially at 400 °C and 800 °C for 1 hour, respectively. The resultant products exhibit high purity in the shape of wavy wire, together with a uniform diameter of 51 ± 5.2 nm and the length in the range of 2-8 μm. Systematic studies have been conducted to investigate the effect of reaction parameters in two activation stages on the morphology and structure of final products. It is worth noting that the as-prepared WCNWs could find promising use in the field of both nanoparticle separation and catalysis. For example, they exhibit outstanding separation abilities towards Au nanospheres with different sizes and enhanced catalytic performance when serving as the catalyst support for Pd towards ethanol oxidation reaction. Particularly, the peak current density of Pd/WCNWs catalysts can reach 2126 mA mg Pd -1 and the value of its electrochemical active surface area is 60.5 m 2 g Pd -1 ., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

Purpose: Obesity is an established risk factor for pelvic floor disorders (PFD) but the effects of bariatric surgery on PFD are uncertain. This meta-analysis was conducted to evaluate the effects of bariatric surgery on PFD in obese women., Methods: A systematic search of PubMed, Cochrane Library, CNKI and CBM databases up to October 2016 was performed, and studies reporting pre-operative and post-operative outcomes in obese women undergoing bariatric surgery were included. The Pelvic Floor Distress Inventory (PFDI-20), the Pelvic Floor Incontinence Questionnaire (PFIQ-7), the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire, Female Sexual Function Index and the International Consultation on Incontinence Questionnaire-Urinary Incontinence short form score were used for evaluating pelvic floor dysfunction after bariatric surgery., Results: Eleven cohort studies were finally included. Pooled results revealed that bariatric surgery was associated with a significant improvement in PFD for obese women on the whole [PFDI-20: SMD = 0.89, 95% CI (0.44, 1.34), P < 0.001; PFIQ-7: SMD = 1.23, 95% CI (0.17, 2.29), P = 0.023]. In the subscale analysis, there was significant improvement in urinary incontinence and pelvic organ prolapse. However, no significant improvement was found in fecal incontinence and sexual function., Conclusions: Bariatric surgery is associated with significant improvement in urinary incontinence, and has a benefit on pelvic organ prolapse for obese women. However, there is no significant improvement in fecal incontinence and sexual function. Further multi-center, large-scale and longer-term randomized controlled trials are needed to confirm these results.

We describe a highly sensitive nanoparticle-based fluorescence resonance energy transfer (FRET) probe developed without using molecular fluorophores as donors and acceptors. The success of this work relies on the strategy that DNA scission was designed to occur to the probe when target presented, which enabled the fluorescence signal "turn-on" of graphene quantum dots (GQDs) and thus quantitative analysis. In particular, amino-modified SiO2 NPs were initially coated by GQDs to form highly emitting SiO2/GQDs, followed by conjunction with DNA functionalized gold nanoparticles (Au NPs-DNA) to form SiO2/GQDs-DNA-Au NPs composite. Owing to the FRET interactions between the GQDs and Au NPs, the fluorescence of GQDs was effectively quenched by Au NPs. When bleomycin (BLM), a model analyte, was mixed with the probe, the fluorescence signal of GQDs would be restored due to the removal of Au NPs from the SiO2/GQDs surface by DNA scission treatment with BLM in the presence of Fe (II). The current FRET probe shows a good linear relationship between the fluorescence intensity and the concentration of BLM in the range from 0.5nM to 1μM with a detection limit of 0.2nM. The probe also shows satisfactory results for the analysis of clinical serum samples. This method provides versatility to the application of GQDs in FRET biosensing and could be potentially extended to other similar systems by replacing the linker between the GQDs and Au NPs., (Copyright © 2016 Elsevier B.V. All rights reserved.)

We report an ultrasensitive electrochemical immunosensor designed for the detection of protein biomarkers using horseradish peroxidase (HRP)-loaded silica-poly(acrylic acid) brushes (SiO2-SPAABs) as labels. HRP could be efficiently and stably accommodated in the three-dimensional architecture of the SiO2-SPAABs and the SiO2-SPAABs-HRP exhibited high catalytic performance towards o-phenylenediamine (OPD) oxidation in the presence of H2O2, which resulted in significant differential pulse voltammetric (DPV) response change and color change. Using human IgG (HIgG) as a model analyte, a sandwich-type immunosensor was constructed. In particular, graphene oxide (GO) and SiO2-SPAABs-HRP were used to immobilize capture antibody (Ab1) and bind a layer of detection antibody (Ab2), respectively. The current biosensor exhibited a good linear response of HIgG from 100pg/mL to 100μg/mL with a detection limit of 50pg/mL (S/N=5). The sensitivity was 6.70-fold higher than the conventional enzyme-linked immunosorbent assays. The immunosensor results were validated through the detection of HIgG in serum samples., (Copyright © 2015 Elsevier B.V. All rights reserved.)

We report a fluorescent turn-on nanoprobe for ultrasensitive detection of prostate specific antigen (PSA) based on graphene oxide quantum dots@silver (GQDs@Ag) core-shell nanocrystals. The success of this work relies on the assembly of quantities of GQDs in one GQDs@Ag probe, which makes the ratio of probe to target significantly increased and thus enables the fluorescent signal enhancement. When the silver shell was removed via oxidative etching using hydrogen peroxide (H2O2), the incorporated GQDs could be readily released and the whole process caused little change to their fluorescence performance. We tested the probe for the ultrasensitive detection of PSA based on the sandwich protocol of immunosensors. In particular, magnetic beads (MBs) were employed to immobilize anti-PSA antibody (Ab1) and acted as a separable capture probe, while GQDs@Ag was used as detection probe by linking antibody (Ab2). The developed immunosensor showed a good linear relationship between the fluorescence intensity and the concentration of PSA in the range from 1 pg/mL to 20 ng/mL with a detection limit of 0.3 pg/mL. The immunosensor used for the analysis of clinical serum samples exhibited satisfactory results, which demonstrated its potential for practical diagnostic applications. This method provides a possible solution to the application of GQDs in immunosensing and could be potentially extended to other similar systems., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A novel colorimetric immunoassay was designed for the sensitive detection of carbohydrate antigen 125 (CA125). The success of this immunoassay relies on the use of hollow polydopamine-gold nanoparticles (PDA-Au) for signal amplification to achieve sensitive nonenzymatic colorimetric detection. In particular, PDA-Au was used as a stable and sensitive label and aminated-Fe3O4 magnetic nanoparticles (Fe3O4 NPs) were employed to immobilize capture antibody (Ab1) and acted as a separable immunosensing probe. PDA-Au exhibited high catalytic performance towards p-nitrophenol reduction and thus resulted in significant color change and UV/vis signal variations. The immunoassay was performed based on sandwich protocol. As compared to pure Au nanoparticles, the signal amplification and sensitivity of PDA-Au-based assay was significantly improved. For instance, the dynamic range of the developed colorimetric immunoassay for CA125 was 0.1-100 U/mL with a detection limit of 0.1 U/mL at S/N=3. In addition, this immunoassay was also tested for the analysis of clinical serum samples, which demonstrated its potential for practical diagnostic applications., (Copyright © 2015 Elsevier B.V. All rights reserved.)

We report our observation of changes to the crystallinity or morphology during seed-mediated growth of Au nanocrystals. When single-crystal Au seeds with a spherical or rod-like shape were treated with a chemical species such as S2O3(2-) ions, twin defects were developed during the growth process to generate multiply twinned nanostructures. X-ray photoelectron spectroscopy analysis indicated that the S2O3(2-) ions were chemisorbed on the surfaces of the seeds during the treatment. The chemisorbed S2O3(2-) ions somehow influenced the crystallization of Au atoms added onto the surface during a growth process, leading to the formation of twin defects. In contrast to the spherical and rod-like Au seeds, the single-crystal structure was retained to generate a concave morphology when single-crystal Au seeds with a cubic or octahedral shape were used for a similar treatment and then seed-mediated growth. The different outcomes are likely related to the difference in spatial distribution of S2O3(2-) ions chemisorbed on the surface of a seed. This approach based on surface modification is potentially extendable to other noble metals for engineering the crystallinity and morphology of nanocrystals formed via seed-mediated growth.

We report a facile synthesis of Au tetrahedra in high purity and with tunable, well-controlled sizes via seed-mediated growth. The success of this synthesis relies on the use of single-crystal, spherical Au nanocrystals as the seeds and manipulation of the reaction kinetics to induce an unsymmetrical growth pattern for the seeds. In particular, the dropwise addition of a precursor solution with a syringe pump, assisted by cetyltrimethylammonium chloride and bromide at appropriate concentrations, was found to be critical to the formation of Au tetrahedra in high purity. Their sizes could be readily tuned in the range of 30-60 nm by simply varying the amount of precursor added to the reaction solution. The current strategy not only enables the synthesis of Au tetrahedra with tunable and controlled sizes but also provides a facile and versatile approach to reducing the symmetry of nanocrystals made of a face-centered cubic lattice., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Palladium octahedra with controlled edge lengths were obtained from Pd cubes of a single size. The success of this synthesis relies on a transformation involving oxidative etching and regrowth. Because the {100} side faces of the Pd nanocubes were capped by Br(-) ions, Pd atoms were removed from the corners during oxidative etching, and the resultant Pd(2+) ions could be reduced and deposited back onto the nanocubes, but preferentially on the {100} facets. We could control the ratio of the etching and regrowth rates (R(etching) and R(regrowth)) simply by varying the amount of HCl added to the reaction solution. With a large amount of HCl, etching dominated the process (R(etching) ≫ R(regrowth)), resulting in the formation of Pd octahedra with an edge length equal to 70% of that of the cubes. In contrast, with a small amount of HCl, all of the newly formed Pd(2+) ions could be quickly reduced and deposited back onto the Pd cubes. In this case, R(etching) ≈ R(regrowth), and the resultant Pd octahedra had roughly the same volume as the starting cubes, together with an edge length equal to 130% of that of the cubes. When the amount of HCl was between these two extremes, we obtained Pd octahedra with intermediate edge lengths. This work not only advances our understanding of oxidative etching in nanocrystal synthesis but also offers a powerful means for controlling the shape and size of metal nanocrystals simply by adjusting the rates of etching and regrowth.

This article describes a facile synthesis of Pd-Ir bimetallic nanostructures in the forms of core-shell octapods and alloyed nanocages. The success of this synthesis relies on the use of Pd nanocubes as the sacrificial templates and interplay of two different processes: the galvanic replacement between an Ir precursor and the Pd nanocubes and the co-reduction of Pd(2+) and Ir(3+) by ethylene glycol. The galvanic replacement played a dominant role in the initial stage, through which Pd atoms were dissolved from the side faces whereas Ir atoms were deposited at the corner sites to generate Pd-Ir core-shell octapods. As the concentration of Pd(2+) in the reaction mixture was increased, co-reduction of Pd(2+) and Ir(3+) occurred in the late stage of synthesis. The resultant Pd and Ir atoms were deposited onto the octapods while the Pd atoms in the interiors continued to be etched away due to the galvanic replacement, finally leading to the formation of Pd-Ir alloyed nanocages. The octapods and nanocages were then evaluated as catalysts for the selective generation of hydrogen from the decomposition of hydrous hydrazine. The nanocages exhibited better selectivity for hydrogen generation than octapods (66% versus 29%), which can be attributed to the presence of an alloyed, porous structure on the surface.

Single-crystal gold nanospheres with controlled diameters in the range 5-30 nm were synthesized by using a facile approach that was based on successive seed-mediated growth. The key to the success of this synthesis was the use of hexadecyltrimethylammonium chloride (CTAC) as a capping agent and a large excess of ascorbic acid as a reductant to ensure fast reduction and, thus, single crystallinity and a spherical shape of the resultant nanoparticles. The diameters of the gold nanospheres could be readily controlled by varying the amount of seeds that were introduced into the reaction system. The gold nanospheres could be produced with uniform diameters of up to 30 nm; thus, their localized surface plasmon resonance properties could be directly compared with the results that were obtained from theoretical calculations. Interestingly, we also found that these gold nanospheres self-assembled into dimers, larger aggregates, and wavy nanowires when they were collected by centrifugation, dispersed in deionized water, and then diluted to different volumes with deionized water., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This article describes a robust method for the facile synthesis of small Ag nanocubes with edge lengths controlled in the range of 18-32 nm. The success of this new method relies on the substitution of ethylene glycol (EG)--the solvent most commonly used in a polyol synthesis--with diethylene glycol (DEG). Owing to the increase in hydrocarbon chain length, DEG possesses a higher viscosity and a lower reducing power relative to EG. As a result, we were able to achieve a nucleation burst in the early stage to generate a large number of seeds and a relatively slow growth rate thereafter; both factors were critical to the formation of Ag nanocubes with small sizes and in high purity (>95%). The edge length of the Ag nanocubes could be easily tailored in the range of 18-32 nm by quenching the reaction at different time points. For the first time, we were able to produce uniform sub-20 nm Ag nanocubes in a hydrophilic medium and on a scale of ∼20 mg per batch. It is also worth pointing out that the present protocol was remarkably robust, showing good reproducibility between different batches and even for DEGs obtained from different vendors. Our results suggest that the high sensitivity of synthesis outcomes to the trace amounts of impurities in a polyol, a major issue for reproducibility and scale up synthesis, did not exist in the present system.

This article reports a systematic study of the seed-mediated growth of Au@Pd core-shell nanocrystals with a variety of controlled sizes and morphologies. The key to the success of this synthesis is to manipulate the reaction kinetics by tuning a set of reaction parameters, including the type and concentration of capping agent, the amount of ascorbic acid used as the reducing agent, and the injection rate used for the precursor solution. Starting from Au nanospheres of 11 nm in diameter as the seeds, Au@Pd core-shell nanocrystals with a number of morphologies, including octahedra, concave octahedra, rectangular bars, cubes, concave cubes, and dendrites, could all be obtained by simply altering the reaction rate. For the first time, it was possible to generate Au@Pd nanocrystals with concave structures on the surfaces while their sizes were kept below 20 nm. In addition, the as-prepared Au@Pd nanocubes can be used as seeds to generate Au@Pd@Au and Au@Pd@Au@Pd nanocrystals with multishelled structures., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The coverage density of poly(ethylene glycol) (PEG) is a key parameter in determining the efficiency of PEGylation, a process pivotal to in vivo delivery and targeting of nanomaterials. Here we report four complementary methods for quantifying the coverage density of PEG chains on various types of Au nanostructures by using a model system based on HS-PEG-NH(2) with different molecular weights. Specifically, the methods involve reactions with fluorescamine and ninhydrin, as well as labeling with fluorescein isothiocyanate (FITC) and Cu(2+) ions. The first two methods use conventional amine assays to measure the number of unreacted HS-PEG-NH(2) molecules left behind in the solution after incubation with the Au nanostructures. The other two methods involve coupling between the terminal -NH(2) groups of adsorbed -S-PEG-NH(2) chains and FITC or a ligand for Cu(2+) ion, and thus pertain to the "active" -NH(2) groups on the surface of a Au nanostructure. We found that the coverage density decreased as the length of PEG chains increased. A stronger binding affinity of the initial capping ligand to the Au surface tended to reduce the PEGylation efficiency by slowing down the ligand exchange process. For the Au nanostructures and capping ligands we have tested, the PEGylation efficiency decreased in the order of citrate-capped nanoparticles > PVP-capped nanocages ≈ CTAC-capped nanoparticles ≫ CTAB-capped nanorods, where PVP, CTAC, and CTAB stand for poly(vinyl pyrrolidone), cetyltrimethylammonium chloride, and cetyltrimethylammonium bromide, respectively., (© 2011 American Chemical Society)

Shaped and dimpled: Silver nanocrystals enclosed by concave surfaces and thus high-index facets have been prepared by simply controlling the growth habit of Ag cubic seeds. Four types of concave nanocrystals, including octahedron, cube, octapod, and trisoctahedron, were obtained (see picture)., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A facile method for generating Au nanorice enclosed by high-index facets in high purity. The nanorice shows much higher catalytic activity for CO oxidation than multiply twinned particles of Au enclosed by {111} facets at temperatures below 300 °C., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This paper provides direct evidence to support the role of a capping agent in controlling the evolution of Ag seeds into nanocrystals with different shapes. Starting with single-crystal seeds (spherical or cubic in shape), we could selectively obtain Ag octahedrons enclosed by {111} facets and nanocubes/nanobars enclosed by {100} facets by adding sodium citrate (Na(3)CA) and poly(vinyl pyrrolidone) (PVP), respectively, as a capping agent while all other parameters were kept the same. This research not only offers new insights into the role played by a capping agent in shape-controlled synthesis but also provides, for the first time, Ag octahedrons as small as 40 nm in edge length for optical and spectroscopic studies.

A high power and efficient 588 nm yellow light is demonstrated through intracavity frequency doubling of an acousto-optic Q-switched self-frequency Raman laser. A 30-mm-length double-end diffusion-bonded Nd:YVO(4) crystal was utilized for efficient self-Raman laser operation by reducing the thermal effects and increasing the interaction length for the stimulated Raman scattering. A 15-mm-length LBO with non-critical phase matching (theta = 90 degrees, phi = 0 degrees) cut was adopted for efficient second-harmonic generation. The focus position of incident pump light and both the repetition rate and the duty cycle of the Q-switch have been optimized. At a repetition rate of 110 kHz and a duty cycle of 5%, the average power of 588 nm light is up to 7.93 W while the incident pump power is 26.5 W, corresponding to an overall diode-yellow conversion efficiency of 30% and a slope efficiency of 43%.

Background: We used an animal model of experimental varicocele to investigate the effects on the ipsilateral testis during the progression of experimental varicocele in rat., Material/methods: Experimental varicocele was induced by partial ligation of the left renal vein in rats. Rats in each control group were subjected to a sham operation. After different periods of varicocele creation (6, 12, and 18 weeks), each animal's left testis was extirpated, and Johnsen's score, ultrastructure of seminiferous tubules, intratesticular testosterone concentration, and the germ cell apoptotic index of each left testis were compared between the experimental and control groups., Results: Johnsen's score and intratesticular testosterone concentrations in each experimental varicocele group were significantly lower than those in the corresponding control groups (P<0.05) and showed significant declines as the duration of varicocele gradually increased; the apoptotic index showed an opposite tendency. Ultrastructural injury of seminiferous tubules gradually became severe as the duration of varicocele gradually increased., Conclusions: Experimental varicocele caused progressive impairment of the ipsilateral testis; apoptosis mediated the pathophysiological processes of dyszoospermia.